I have a 1991 Ford E250. This morning the heater/AC fan did not work on
any setting. Later in the morning I tried the fan again and it worked
on all three settings but after the fan is set to medium or high
setting the fan gradually slows down to the low setting speed after
about 5 seconds. It will blow continously but at the lower speed. Does
any body have a sugestion of how to fix the problem?